1
linux/net/sunrpc/auth_gss/gss_krb5_wrap.c
J. Bruce Fields c52226daf5 rpc: handle rotated gss data for Windows interoperability
The data in Kerberos gss tokens can be rotated.  But we were lazy and
rejected any nonzero rotation value.  It wasn't necessary for the
implementations we were testing against at the time.

But it appears that Windows does use a nonzero value here.

So, implement rotation to bring ourselves into compliance with the spec
and to interoperate with Windows.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2012-05-31 20:29:39 -04:00

617 lines
17 KiB
C

/*
* COPYRIGHT (c) 2008
* The Regents of the University of Michigan
* ALL RIGHTS RESERVED
*
* Permission is granted to use, copy, create derivative works
* and redistribute this software and such derivative works
* for any purpose, so long as the name of The University of
* Michigan is not used in any advertising or publicity
* pertaining to the use of distribution of this software
* without specific, written prior authorization. If the
* above copyright notice or any other identification of the
* University of Michigan is included in any copy of any
* portion of this software, then the disclaimer below must
* also be included.
*
* THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
* FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
* PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
* MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
* WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
* REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
* FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
* CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
* OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
* IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGES.
*/
#include <linux/types.h>
#include <linux/jiffies.h>
#include <linux/sunrpc/gss_krb5.h>
#include <linux/random.h>
#include <linux/pagemap.h>
#include <linux/crypto.h>
#ifdef RPC_DEBUG
# define RPCDBG_FACILITY RPCDBG_AUTH
#endif
static inline int
gss_krb5_padding(int blocksize, int length)
{
return blocksize - (length % blocksize);
}
static inline void
gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
{
int padding = gss_krb5_padding(blocksize, buf->len - offset);
char *p;
struct kvec *iov;
if (buf->page_len || buf->tail[0].iov_len)
iov = &buf->tail[0];
else
iov = &buf->head[0];
p = iov->iov_base + iov->iov_len;
iov->iov_len += padding;
buf->len += padding;
memset(p, padding, padding);
}
static inline int
gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
{
u8 *ptr;
u8 pad;
size_t len = buf->len;
if (len <= buf->head[0].iov_len) {
pad = *(u8 *)(buf->head[0].iov_base + len - 1);
if (pad > buf->head[0].iov_len)
return -EINVAL;
buf->head[0].iov_len -= pad;
goto out;
} else
len -= buf->head[0].iov_len;
if (len <= buf->page_len) {
unsigned int last = (buf->page_base + len - 1)
>>PAGE_CACHE_SHIFT;
unsigned int offset = (buf->page_base + len - 1)
& (PAGE_CACHE_SIZE - 1);
ptr = kmap_atomic(buf->pages[last]);
pad = *(ptr + offset);
kunmap_atomic(ptr);
goto out;
} else
len -= buf->page_len;
BUG_ON(len > buf->tail[0].iov_len);
pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
out:
/* XXX: NOTE: we do not adjust the page lengths--they represent
* a range of data in the real filesystem page cache, and we need
* to know that range so the xdr code can properly place read data.
* However adjusting the head length, as we do above, is harmless.
* In the case of a request that fits into a single page, the server
* also uses length and head length together to determine the original
* start of the request to copy the request for deferal; so it's
* easier on the server if we adjust head and tail length in tandem.
* It's not really a problem that we don't fool with the page and
* tail lengths, though--at worst badly formed xdr might lead the
* server to attempt to parse the padding.
* XXX: Document all these weird requirements for gss mechanism
* wrap/unwrap functions. */
if (pad > blocksize)
return -EINVAL;
if (buf->len > pad)
buf->len -= pad;
else
return -EINVAL;
return 0;
}
void
gss_krb5_make_confounder(char *p, u32 conflen)
{
static u64 i = 0;
u64 *q = (u64 *)p;
/* rfc1964 claims this should be "random". But all that's really
* necessary is that it be unique. And not even that is necessary in
* our case since our "gssapi" implementation exists only to support
* rpcsec_gss, so we know that the only buffers we will ever encrypt
* already begin with a unique sequence number. Just to hedge my bets
* I'll make a half-hearted attempt at something unique, but ensuring
* uniqueness would mean worrying about atomicity and rollover, and I
* don't care enough. */
/* initialize to random value */
if (i == 0) {
i = random32();
i = (i << 32) | random32();
}
switch (conflen) {
case 16:
*q++ = i++;
/* fall through */
case 8:
*q++ = i++;
break;
default:
BUG();
}
}
/* Assumptions: the head and tail of inbuf are ours to play with.
* The pages, however, may be real pages in the page cache and we replace
* them with scratch pages from **pages before writing to them. */
/* XXX: obviously the above should be documentation of wrap interface,
* and shouldn't be in this kerberos-specific file. */
/* XXX factor out common code with seal/unseal. */
static u32
gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
struct xdr_buf *buf, struct page **pages)
{
char cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
struct xdr_netobj md5cksum = {.len = sizeof(cksumdata),
.data = cksumdata};
int blocksize = 0, plainlen;
unsigned char *ptr, *msg_start;
s32 now;
int headlen;
struct page **tmp_pages;
u32 seq_send;
u8 *cksumkey;
u32 conflen = kctx->gk5e->conflen;
dprintk("RPC: %s\n", __func__);
now = get_seconds();
blocksize = crypto_blkcipher_blocksize(kctx->enc);
gss_krb5_add_padding(buf, offset, blocksize);
BUG_ON((buf->len - offset) % blocksize);
plainlen = conflen + buf->len - offset;
headlen = g_token_size(&kctx->mech_used,
GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength + plainlen) -
(buf->len - offset);
ptr = buf->head[0].iov_base + offset;
/* shift data to make room for header. */
xdr_extend_head(buf, offset, headlen);
/* XXX Would be cleverer to encrypt while copying. */
BUG_ON((buf->len - offset - headlen) % blocksize);
g_make_token_header(&kctx->mech_used,
GSS_KRB5_TOK_HDR_LEN +
kctx->gk5e->cksumlength + plainlen, &ptr);
/* ptr now at header described in rfc 1964, section 1.2.1: */
ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);
msg_start = ptr + GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength;
*(__be16 *)(ptr + 2) = cpu_to_le16(kctx->gk5e->signalg);
memset(ptr + 4, 0xff, 4);
*(__be16 *)(ptr + 4) = cpu_to_le16(kctx->gk5e->sealalg);
gss_krb5_make_confounder(msg_start, conflen);
if (kctx->gk5e->keyed_cksum)
cksumkey = kctx->cksum;
else
cksumkey = NULL;
/* XXXJBF: UGH!: */
tmp_pages = buf->pages;
buf->pages = pages;
if (make_checksum(kctx, ptr, 8, buf, offset + headlen - conflen,
cksumkey, KG_USAGE_SEAL, &md5cksum))
return GSS_S_FAILURE;
buf->pages = tmp_pages;
memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);
spin_lock(&krb5_seq_lock);
seq_send = kctx->seq_send++;
spin_unlock(&krb5_seq_lock);
/* XXX would probably be more efficient to compute checksum
* and encrypt at the same time: */
if ((krb5_make_seq_num(kctx, kctx->seq, kctx->initiate ? 0 : 0xff,
seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8)))
return GSS_S_FAILURE;
if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
struct crypto_blkcipher *cipher;
int err;
cipher = crypto_alloc_blkcipher(kctx->gk5e->encrypt_name, 0,
CRYPTO_ALG_ASYNC);
if (IS_ERR(cipher))
return GSS_S_FAILURE;
krb5_rc4_setup_enc_key(kctx, cipher, seq_send);
err = gss_encrypt_xdr_buf(cipher, buf,
offset + headlen - conflen, pages);
crypto_free_blkcipher(cipher);
if (err)
return GSS_S_FAILURE;
} else {
if (gss_encrypt_xdr_buf(kctx->enc, buf,
offset + headlen - conflen, pages))
return GSS_S_FAILURE;
}
return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
}
static u32
gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
{
int signalg;
int sealalg;
char cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
struct xdr_netobj md5cksum = {.len = sizeof(cksumdata),
.data = cksumdata};
s32 now;
int direction;
s32 seqnum;
unsigned char *ptr;
int bodysize;
void *data_start, *orig_start;
int data_len;
int blocksize;
u32 conflen = kctx->gk5e->conflen;
int crypt_offset;
u8 *cksumkey;
dprintk("RPC: gss_unwrap_kerberos\n");
ptr = (u8 *)buf->head[0].iov_base + offset;
if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
buf->len - offset))
return GSS_S_DEFECTIVE_TOKEN;
if ((ptr[0] != ((KG_TOK_WRAP_MSG >> 8) & 0xff)) ||
(ptr[1] != (KG_TOK_WRAP_MSG & 0xff)))
return GSS_S_DEFECTIVE_TOKEN;
/* XXX sanity-check bodysize?? */
/* get the sign and seal algorithms */
signalg = ptr[2] + (ptr[3] << 8);
if (signalg != kctx->gk5e->signalg)
return GSS_S_DEFECTIVE_TOKEN;
sealalg = ptr[4] + (ptr[5] << 8);
if (sealalg != kctx->gk5e->sealalg)
return GSS_S_DEFECTIVE_TOKEN;
if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
return GSS_S_DEFECTIVE_TOKEN;
/*
* Data starts after token header and checksum. ptr points
* to the beginning of the token header
*/
crypt_offset = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) -
(unsigned char *)buf->head[0].iov_base;
/*
* Need plaintext seqnum to derive encryption key for arcfour-hmac
*/
if (krb5_get_seq_num(kctx, ptr + GSS_KRB5_TOK_HDR_LEN,
ptr + 8, &direction, &seqnum))
return GSS_S_BAD_SIG;
if ((kctx->initiate && direction != 0xff) ||
(!kctx->initiate && direction != 0))
return GSS_S_BAD_SIG;
if (kctx->enctype == ENCTYPE_ARCFOUR_HMAC) {
struct crypto_blkcipher *cipher;
int err;
cipher = crypto_alloc_blkcipher(kctx->gk5e->encrypt_name, 0,
CRYPTO_ALG_ASYNC);
if (IS_ERR(cipher))
return GSS_S_FAILURE;
krb5_rc4_setup_enc_key(kctx, cipher, seqnum);
err = gss_decrypt_xdr_buf(cipher, buf, crypt_offset);
crypto_free_blkcipher(cipher);
if (err)
return GSS_S_DEFECTIVE_TOKEN;
} else {
if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
return GSS_S_DEFECTIVE_TOKEN;
}
if (kctx->gk5e->keyed_cksum)
cksumkey = kctx->cksum;
else
cksumkey = NULL;
if (make_checksum(kctx, ptr, 8, buf, crypt_offset,
cksumkey, KG_USAGE_SEAL, &md5cksum))
return GSS_S_FAILURE;
if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
kctx->gk5e->cksumlength))
return GSS_S_BAD_SIG;
/* it got through unscathed. Make sure the context is unexpired */
now = get_seconds();
if (now > kctx->endtime)
return GSS_S_CONTEXT_EXPIRED;
/* do sequencing checks */
/* Copy the data back to the right position. XXX: Would probably be
* better to copy and encrypt at the same time. */
blocksize = crypto_blkcipher_blocksize(kctx->enc);
data_start = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) +
conflen;
orig_start = buf->head[0].iov_base + offset;
data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
memmove(orig_start, data_start, data_len);
buf->head[0].iov_len -= (data_start - orig_start);
buf->len -= (data_start - orig_start);
if (gss_krb5_remove_padding(buf, blocksize))
return GSS_S_DEFECTIVE_TOKEN;
return GSS_S_COMPLETE;
}
/*
* We can shift data by up to LOCAL_BUF_LEN bytes in a pass. If we need
* to do more than that, we shift repeatedly. Kevin Coffman reports
* seeing 28 bytes as the value used by Microsoft clients and servers
* with AES, so this constant is chosen to allow handling 28 in one pass
* without using too much stack space.
*
* If that proves to a problem perhaps we could use a more clever
* algorithm.
*/
#define LOCAL_BUF_LEN 32u
static void rotate_buf_a_little(struct xdr_buf *buf, unsigned int shift)
{
char head[LOCAL_BUF_LEN];
char tmp[LOCAL_BUF_LEN];
unsigned int this_len, i;
BUG_ON(shift > LOCAL_BUF_LEN);
read_bytes_from_xdr_buf(buf, 0, head, shift);
for (i = 0; i + shift < buf->len; i += LOCAL_BUF_LEN) {
this_len = min(LOCAL_BUF_LEN, buf->len - (i + shift));
read_bytes_from_xdr_buf(buf, i+shift, tmp, this_len);
write_bytes_to_xdr_buf(buf, i, tmp, this_len);
}
write_bytes_to_xdr_buf(buf, buf->len - shift, head, shift);
}
static void _rotate_left(struct xdr_buf *buf, unsigned int shift)
{
int shifted = 0;
int this_shift;
shift %= buf->len;
while (shifted < shift) {
this_shift = min(shift - shifted, LOCAL_BUF_LEN);
rotate_buf_a_little(buf, this_shift);
shifted += this_shift;
}
}
static void rotate_left(u32 base, struct xdr_buf *buf, unsigned int shift)
{
struct xdr_buf subbuf;
xdr_buf_subsegment(buf, &subbuf, base, buf->len - base);
_rotate_left(&subbuf, shift);
}
static u32
gss_wrap_kerberos_v2(struct krb5_ctx *kctx, u32 offset,
struct xdr_buf *buf, struct page **pages)
{
int blocksize;
u8 *ptr, *plainhdr;
s32 now;
u8 flags = 0x00;
__be16 *be16ptr, ec = 0;
__be64 *be64ptr;
u32 err;
dprintk("RPC: %s\n", __func__);
if (kctx->gk5e->encrypt_v2 == NULL)
return GSS_S_FAILURE;
/* make room for gss token header */
if (xdr_extend_head(buf, offset, GSS_KRB5_TOK_HDR_LEN))
return GSS_S_FAILURE;
/* construct gss token header */
ptr = plainhdr = buf->head[0].iov_base + offset;
*ptr++ = (unsigned char) ((KG2_TOK_WRAP>>8) & 0xff);
*ptr++ = (unsigned char) (KG2_TOK_WRAP & 0xff);
if ((kctx->flags & KRB5_CTX_FLAG_INITIATOR) == 0)
flags |= KG2_TOKEN_FLAG_SENTBYACCEPTOR;
if ((kctx->flags & KRB5_CTX_FLAG_ACCEPTOR_SUBKEY) != 0)
flags |= KG2_TOKEN_FLAG_ACCEPTORSUBKEY;
/* We always do confidentiality in wrap tokens */
flags |= KG2_TOKEN_FLAG_SEALED;
*ptr++ = flags;
*ptr++ = 0xff;
be16ptr = (__be16 *)ptr;
blocksize = crypto_blkcipher_blocksize(kctx->acceptor_enc);
*be16ptr++ = cpu_to_be16(ec);
/* "inner" token header always uses 0 for RRC */
*be16ptr++ = cpu_to_be16(0);
be64ptr = (__be64 *)be16ptr;
spin_lock(&krb5_seq_lock);
*be64ptr = cpu_to_be64(kctx->seq_send64++);
spin_unlock(&krb5_seq_lock);
err = (*kctx->gk5e->encrypt_v2)(kctx, offset, buf, ec, pages);
if (err)
return err;
now = get_seconds();
return (kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE;
}
static u32
gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
{
s32 now;
u64 seqnum;
u8 *ptr;
u8 flags = 0x00;
u16 ec, rrc;
int err;
u32 headskip, tailskip;
u8 decrypted_hdr[GSS_KRB5_TOK_HDR_LEN];
unsigned int movelen;
dprintk("RPC: %s\n", __func__);
if (kctx->gk5e->decrypt_v2 == NULL)
return GSS_S_FAILURE;
ptr = buf->head[0].iov_base + offset;
if (be16_to_cpu(*((__be16 *)ptr)) != KG2_TOK_WRAP)
return GSS_S_DEFECTIVE_TOKEN;
flags = ptr[2];
if ((!kctx->initiate && (flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)) ||
(kctx->initiate && !(flags & KG2_TOKEN_FLAG_SENTBYACCEPTOR)))
return GSS_S_BAD_SIG;
if ((flags & KG2_TOKEN_FLAG_SEALED) == 0) {
dprintk("%s: token missing expected sealed flag\n", __func__);
return GSS_S_DEFECTIVE_TOKEN;
}
if (ptr[3] != 0xff)
return GSS_S_DEFECTIVE_TOKEN;
ec = be16_to_cpup((__be16 *)(ptr + 4));
rrc = be16_to_cpup((__be16 *)(ptr + 6));
seqnum = be64_to_cpup((__be64 *)(ptr + 8));
if (rrc != 0)
rotate_left(offset + 16, buf, rrc);
err = (*kctx->gk5e->decrypt_v2)(kctx, offset, buf,
&headskip, &tailskip);
if (err)
return GSS_S_FAILURE;
/*
* Retrieve the decrypted gss token header and verify
* it against the original
*/
err = read_bytes_from_xdr_buf(buf,
buf->len - GSS_KRB5_TOK_HDR_LEN - tailskip,
decrypted_hdr, GSS_KRB5_TOK_HDR_LEN);
if (err) {
dprintk("%s: error %u getting decrypted_hdr\n", __func__, err);
return GSS_S_FAILURE;
}
if (memcmp(ptr, decrypted_hdr, 6)
|| memcmp(ptr + 8, decrypted_hdr + 8, 8)) {
dprintk("%s: token hdr, plaintext hdr mismatch!\n", __func__);
return GSS_S_FAILURE;
}
/* do sequencing checks */
/* it got through unscathed. Make sure the context is unexpired */
now = get_seconds();
if (now > kctx->endtime)
return GSS_S_CONTEXT_EXPIRED;
/*
* Move the head data back to the right position in xdr_buf.
* We ignore any "ec" data since it might be in the head or
* the tail, and we really don't need to deal with it.
* Note that buf->head[0].iov_len may indicate the available
* head buffer space rather than that actually occupied.
*/
movelen = min_t(unsigned int, buf->head[0].iov_len, buf->len);
movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen >
buf->head[0].iov_len);
memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen);
buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip;
buf->len -= GSS_KRB5_TOK_HDR_LEN + headskip;
return GSS_S_COMPLETE;
}
u32
gss_wrap_kerberos(struct gss_ctx *gctx, int offset,
struct xdr_buf *buf, struct page **pages)
{
struct krb5_ctx *kctx = gctx->internal_ctx_id;
switch (kctx->enctype) {
default:
BUG();
case ENCTYPE_DES_CBC_RAW:
case ENCTYPE_DES3_CBC_RAW:
case ENCTYPE_ARCFOUR_HMAC:
return gss_wrap_kerberos_v1(kctx, offset, buf, pages);
case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
return gss_wrap_kerberos_v2(kctx, offset, buf, pages);
}
}
u32
gss_unwrap_kerberos(struct gss_ctx *gctx, int offset, struct xdr_buf *buf)
{
struct krb5_ctx *kctx = gctx->internal_ctx_id;
switch (kctx->enctype) {
default:
BUG();
case ENCTYPE_DES_CBC_RAW:
case ENCTYPE_DES3_CBC_RAW:
case ENCTYPE_ARCFOUR_HMAC:
return gss_unwrap_kerberos_v1(kctx, offset, buf);
case ENCTYPE_AES128_CTS_HMAC_SHA1_96:
case ENCTYPE_AES256_CTS_HMAC_SHA1_96:
return gss_unwrap_kerberos_v2(kctx, offset, buf);
}
}